Scaling, corrosion, precipitates, and material defects are some problems faced by the oil and gas industry when managing production well and pipeline assets. These problems lead to diminished production in wells, casing integrity failure, and pipeline integrity failure any of which may result in costly and complex remediation measures. As such, electromagnetic techniques are commonly used to monitor the condition of the production and intermediate casing strings, tubings, collars, filters, packers, and perforations. These techniques can measure magnetic field data to obtain accurate measurements of tubing thickness and tubing corrosion.
This form of corrosion monitoring can be especially useful to prevent pipe integrity failures in mature wells or non-producing wells. For example, corrosion damage typically decreases the thickness of casing strings. One electromagnetic technique used for defect detection is the pulse eddy current technique. In this technique, when a transmitter coil emits a primary electromagnetic field, or signal, eddy currents are produced in the tubings. The eddy currents produce secondary fields or signals. The transmitter coil is deactivated and/or the excitation signal is turned off and experiences a fall time. Next, a receiver coil, which has hitherto been deactivated, is activated, and the secondary signals are received by the receiver coil. When recorded and processed, the data resulting from the secondary signals can be employed to perform an evaluation of the tubings.
The eddy current technique described above is performed frequently by downhole tool as it is conveyed along a borehole. Accordingly, small inefficiencies such as minor additional power usage and slight delays in the technique become large inefficiencies such as excess power usage and significant unproductive time over the course of the run by the downhole tool and even larger inefficiencies over the lifetime of the tool.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.